Ultrasonic surgical instruments are finding increasingly widespread applications in surgical procedures by virtue of the unique performance characteristics of such instruments. Depending on specific instrument configurations and operational parameters, ultrasonic surgical instruments can provide increased control while significantly reducing surgeon effort and fatigue. Ultrasonic surgical instruments can help reduce surgeon effort during bone shaving, and reduce the force required to penetrate tissue, for example, when inserting a trocar through the abdominal wall of a patient.
Ultrasonic trocar obturators may be used to reduce the force necessary to penetrate the abdominal wall during laparoscopic surgery. Such a device is disclosed in U.S. Pat. No. 5,449,370, which describes using ultrasonic energy to assist in the insertion of a trocar obturator and cannula into a body cavity through, for example, the abdominal wall of a human being, providing access to internal organs or other tissue.
Ultrasonic devices for removing bone cement tubes during prosthesis replacements have been developed. U.S. Pat. Nos.: 5,019,083; 5,413,578; and 5,318,570 describe the need to reduce the force necessary when removing bone cement used for prosthesis fixation, and to increase the surgeons control during the removal process. The ultrasonic devices described in U.S. Pat. Nos. 5,019,083; 5,413,578; and 5,318,570 are designed to loosen, or fracture, cement while leaving the bone intact.
Bone anchors and bone anchor insertion devices have been described in, for example, U.S. Pat. No. 5,522,845, which describes a bone anchor and a bone anchor insertion tool. In U.S. Pat. No. 5,522,845, a bone anchor insertion tool is used to insert a specially adapted bone anchor into a pre-drilled hole. The bone anchor described in U.S. Pat. No. 5,522,845 includes a suture placed through a bore in the body of the bone anchor. The insertion device funnels and protects the suture from damage during the insertion of the bone anchor into the bone. The bone anchor described in U.S. Pat. No. 5,522,845 also includes barbs protruding from its body. The barbs are used to retain the anchor in the pre-drilled hole. The pre-drilled hole is designed to have a diameter larger than the diameter of the maximum cross-section of the bone anchor in order to reduce the insertion force required to insert the anchor into the bone.
Bone anchors, after insertion into bone, are designed to remain in place and provide a platform for holding tissue. Bone anchors which include a wide spaced multiple turn thread on the outer surface of the bone anchor body have been described in, for example, U.S. Pat. No. 5,411,523. The teaching of U.S. Pat. No. 5,411,523 provides a strong union, or purchase, between the bone and the anchor whereby the anchor is driven clockwise to insert the bone anchor into a pre-drilled hole (i.e. a right-handed screw thread). Counter-clockwise rotation is used to disconnect the bone anchor from the insertion device. Additionally U.S. Pat. No. 5,411,523 describes a bone anchor with a center longitudinal screw thread hole also containing right-handed screw threads.
Bone anchor insertion devices have also been described in, for example, U.S. Pat. No. 5,662,658, which describes a bone anchor and driver contained within a sleeve. The sleeve is connected to a handle with an actuator operative from the handle. In U.S. Pat. No. 5,662,658 the actuator is used to move the driver axially and insert the bone anchor into a previously drilled hole.
It would, therefore, be advantageous to provide an improved bone anchor which is adapted for use with an ultrasonic bone anchor embedding device. Further, it would be advantageous to provide an improved bone anchor, where barbs are not necessary to provide solid fixation of the anchor into the bone. It would also be advantageous to provide a bone anchor capable of being embedded into bone without the need for a pre-drilled pilot hole. It would further be advantageous to provide a bone anchor which can be driven into a pre-drilled pilot hole that is equal to or smaller in diameter than the diameter of the bone anchor. It would also be advantageous to design a bone anchor of a polymeric material which may be driven into a pre-drilled hole which is equal to or smaller than the outer diameter of the bone anchor.